Low temperature separating units



June 28, 1955 c D YO N ETAL 2,711,826

LOW TEMPERATURE SEPARATING UNITS Filed Aug. 50, 1951 s zo O ago Robert W. Coggins INVENTOR ATTORNEY United States Patent LOW TEMPERATURE SEPARATING UNITS Charles Edward DeYoung, Lake Charles, La., and Robert W. Coggins, Tulsa, Okla., assignors to National Tank Company, Tulsa, Okla., a corporation of Nevada Application August 30, 1951, Serial No. 244,406

8 Claims. (Cl. 210-525) This invention relates to new and useful improvements in low temperature separation units.

The invention is particularly concerned with low temperature separation units as employed in the petroleum industry for separation of liquid hydrocarbons and gas, specifically distillate and gas separation, and is directed toward improvements in such units which permit the retention of control of the gas hydrates and/or ice normally formed therein.

The invention, in some respects, is an improvement upon the low temperature unit disclosed in the patent application of Jay P. Walker et al., Serial No. 185,608, filed September 19, 1950 and now abandoned. This improvement, however, is not limited to use with the aforesaid unit and may be employed with other structures and devices.

In low temperature separating units, a well stream composed principally of hydrocarbon gas, liquefiable hydrocarbons and water or water vapor, is separated into its constituent components, a large portion of the water present being reduced to a liquid form, and substantially all of the normally liquefiable hydrocarbons being likewise reduced to a liquid state. The hydrocarbon gas is separated and drawn off, and the water and liquid hydrocarbons are allowed to stratify whereby they may be withdrawn either separately or conjointly. Because of the low temperatures customarily employed in units of this type, quantities of the hydrocarbons, either normally gaseous or normally liquid, combine with the water to form gas hydrates. There may or may not be the simultaneous occurrence of frozen water or ice. It is desirable that the gas hydrates and/or ice be melted and reduced to a liquid state before withdrawal from the unit. It is, therefore, a principal object of this invention to insure that the gas hydrates and/or ice are liquefied before removal from the low temperature separation unit.

A further object of the invention is to provide an improvement for low temperature separation units wherein gas hydrates and/or ice particles are excluded from the liquid removal zone whereby the entry or accumulation of said particles in said zone is prevented.

A particular object of the invention is to provide an improvement for low temperature separation units having means for heating to melt gasv hydrate and/or ice particles, the improvement serving to force the hydrate or ice particles into close proximity with the heating means whereby the melting of said particles is insured.

Yet another object of the invention is to provide an improvement for low temperature separation units having provision for the accumulation of a body of water and a body of liquid hydrocarbon with means in the water layer for supplying heat to melt gas hydrate and/or ice particles, the improvement forcing such particles to enter into the relatively warm water layer before said particles can pass into the liquid removal zone of the unit whereby melting of the particles is insured in the course of their passage to said liquid removal zone.

Still another object of the invetnion is to provide an 'ice improvement of the character described wherein the fluid passing to the liquid removal zone is strained, as through a foraminous member, whereby the passage of gas hydrate and/or ice particles to the liquid removal zone is prevented while the passage of liquid is permitted.

A construction designed to carry out the invention will be hereinafter described together with other features of the invention.

The invention will be more readily understood from a reading of the specification and by reference to the accompanying drawing, wherein an example of the invention is shown, and wherein:

Fig. l is a vertical, longitudinal, sectional view of a low temperature separation unit having incorporated therein the improvement forming the subject matter of this invention,

Fig. 2 is a vertical, cross-sectional view taken upon the line 2-2 of Fig. 1,

Fig. 3 is an enlarged vertical, sectional view taken upon the line 3-3 of Fig. l, and

Fig. 4 is a fragmentary, horizontal, transverse, sectional view taken upon the line 44 of Fig. 1.

In the drawing, the numeral 19 designates a low temperature separation unit which may be of any suitable or desirable type or design. The particular low temperature unit illustrated in the drawings is similar in many respects to that disclosed in the aforementioned application of Jay P. Walker et al., and reference is made to that patent application.

In general, the unit includes an elongate cylindrical tank or vessel 11 having its ends closed by suitable heads 12 and 13 and being supported upon legs 14.

In the specific embodiment illustrated, the fluid stream enters the vessel 11 at one end through a spinner structure 15, the liquid and solid particles from the stream falling into the lower portion or bottom of said vessel. A suitable heating coil 16 is provided in the lower portion of the vessel for supplying heat thereto and melting any gas hydrate or ice particles which may be formed. The liquid Water and hydrocarbons of course settle in the bottom of the tank 11 and stratify therein in accordance with their respective densities.

At the opposite end of the tank 11, there is provided a transverse baflle or weir plate 17 which maintains a predetermined water level in the vessel. The water spills over the upper edge of the baflie 17 and is removed through a suitable outlet 18.

For maintaining a predetermined hydrocarbon liquid level, there is a transverse, rectangular, open-top trough 19 extending across the vessel 11 between the baflie 17 and the ends of the heating coils 16. The side wall of the box 19 adjacent the ends of the coils 16 has its upper edge disposed in a horizontal plane above the horizontal plane of the upper edge of the bafile 17, and liquid hydrocarbons may spill over the upper edge of said wall or weir member of the box 19 into the interior of the box. From the box, the liquid hydrocarbons are removed through a suitable outlet fitting 20. Of course, any suitable type of control may be employed for controlling flow through the outlets 18 and 20.

The structure described has been shown in a somewhat simplified manner, and it is not thought necessary to go into all of the details of arrangement and operation. As a background for a more specific description of the present invention, it is thought sufficient to point out that this separation units operates by reducing the temperature of the flow stream in order that high liquefaction may be obtained. The liquefield water and hydrocarbon components naturally stratify, and provision is made for maintaining a body of these liquids within the vessel. The heating coil immersed in this body of liquids supplies heat for melting the gas hydrate and/ or ice particles which may be formed, the ultimate purpose being the removalof the water and hydrocarbons in a liquid state only. Of course, the gaseous hydrocarbons may be withdrawn in any suitable manner as by the gas outlet 21 in the upper portion of the vessel 11.

Gas hydrates, being of a complex and extremely variable nature, may vary somewhat in density, and it is presently thought possible that some of the hydrates float upon the upper surface of the hydrocarbon layer, while others of the hydrates float at the innerface between the hydrocarbon and water layers. In any event, as the liquids slowly drain toward the outlet end of the vessel 11, the hydrates and/or ice floating in said liquids also move slowly toward the outlet end of the vessel. It is a purpose of these units thatthe frozen particles will be melted by the heating coils 16 before they reach the liquid outlets, and hence, that no frozen particles will pass into the box 19 or over the upper edge of the baffle 17. This, however, does not always occur, and it sometimes happens that the frozen particles enter into the box 19-01' other outlet provision. Manifestly, such a condition is undesirable since the particles are then more or less isolated from the heating coils 16 and may cause ultimate clogging or stoppage of the box 19 or the drain connection 20. The present invention is specifically directed to preventing such an occurrence.

The invention includes a transverse supporting and barrier or baflle member 22 extending horizontally across the vessel 11 above the coils 16 and spaced from the box 19 a short distance toward the inlet end of the vessel. the member 22 may be of any suitable or desirable style or design, it is important that it extend entirely across the vessel and that it intersect the hydrocarbon liquid level in the vessel. In other words, the upper edge of the member 22 is disposed above the hydrocarbon liquid level, while the lower edge of the member 22 is disposed below said liquid level. In this manner, the hydrocarbon liquid, with or without frozen particles therein, is prevented from flowing over the upper edge of the member 22, and in order for the liquid to reach the box 19 and flow over the upper edge thereof, it must flow under the lower edge of the member 22 into close juxtaposition with the heating coils 16. Desirably, the lower edge of the member 22 is situated closely adjacent or slightly above the innerface between the hydrocarbon liquid layer and the water layer, whereby the exiting hydrocarbons and frozen particles are forced into close proximity with the water layer. The favorable heat transfer characteristics of water are thus employed in supplying heat to the frozen particles for melting the same, and it is apparent that no frozen particles -;i

can reach the box 19 without passing in close proximity to the heating coils and to the warm layer of water, whereby melting of said particles is virtually assured.

As a further safeguard against the entry of frozen particles into the outlet, there is provided a perforated or foraminous plate 23 extending transversely of the tank in a horizontal plane and having its lateral edges abutting or in close proximity to the side walls of the member 22 and the box 19. The plate 23 may desirably be supported upon flanges 24 and 25 formed, respectively, upon the member 22 and the box 19, and hence, the plate 23 may be removed when desired by simply lifting it from engagement with said flanges. A suitable handle 26 is provided in the central portion of the plate for this purpose. .The plate 23 carries a multiplicity of small perforations or openings 27 through which the liquid hydrocarbon must flow before passing over the upper edge of the front wall of the box 19. With this arrangement, the plate 23 functions in the manner of a strainer and effectively prevents the entry of frozen particles into the box 19. Any such particles which are slow in melting during their passage around the lower edge of the member 22 will be retarded by-the plate 23 and held in close proximity to the coils 16.

until melting is completed.

-Fror n the foregoing, it will be seen that the invention prevents the entry of frozen particles from the upper por- While lid tion of the hydrocarbon layerdirectly into the outlet, and' instead, forces the frozen particles to move into the lower portion of said hydrocarbon'layer where melting of the particles is more effectively carried out. In addition, a straining of the effluent hydrocarbon liquids is provided while the frozen particles are retarded in order to provide sulficient melting time in the melting zone of the unit.

The foregoing description of the invention is explanatory thereof and various changes in the size, shape and materials, as well as in the detailsof-theillustrated construction may be made, within the scope of -the -appendcd claims, without departing from the spirit of the invention.

What We claim and desire to secure by Letters Patent is:

l. A low temperature separation unit including the combination of, a vessel having a fluid stream inlet for admitting to the vessel a fluid stream containing liquid hydrocarbons and hydrocarbon gas hydrates, a liquid hydrocarbon outlet from the vessel spaced a substantial distance downstream from theinlet, means for maintaining in the vessel a stratum of water separated from the lluid stream, means for maintaining in the vessel a hydrocarbon stratum floating on the water stratum and haying its surface at a sutficient elevation to flow into the liquid hydrocarbon outlet, means in the lower portion of the vessel for supplying heat to the water and hydrocarbonstrata between the inlet and outlet to melt the hydrates therein, and a barrier member mounted in the vessel and isolating the surface of the hydrocarbon stratum upstream of the outlet from the portion of the surface of the hydrocarbon stratum immediately adjacent the outlct, the barrier member extending above the elevation of the outlet at all points between said outlet and the surface of the hydrocarbon stratum upstream of the outlet and haviug at least a portion of its lower extremity terminating in the hydrocarbon stratum above the interface between the hydrocarbon and water strata, whereby hydrocarbons may flow under the barrier member to the outlet, and'a gas outlet from the vessel.

2. A low temperature separation unit as set forth in claim 1 wherein the lower extremity of the barrier memher is disposed above and closely adjacent the means for supplying heat so as to cause hydrocarbons flowing under the barrier member to the outlet to pass in close proximity to said means for supplying heat.

3. A low temperature separation unit as set forth in claim 1 wherein the liquid hydrocarbonoutlet from the surface of the hydrocarbon stratum includes a'partition member over the upper edge ofwhich the liquid'hydrocarbons spill, the barrier member being disposed adjacent said partition member.

4. A low temperature separation unit as set forth in claim 3. flanges on the barrier member and the partition member, and a foraminous plate supported onsaid flanges and extending between the latter members.

5. A low temperature separation unit as set forth in claim 3, and a foraminous plate extending between the barrier member and the partition member.

6. A low temperature separation unit asset forth in claim 5 wherein the foraminous plate is disposed beneath the surface of the hydrocarbon stratum.

7. in a low temperature-separation unit constructed and'arranged to receive a well stream containing hydrocarbons and hydrocarbon gas hydrates, to separate thewell stream into an aqueous and a liquid hydrocarbon phase, and to stratify said phases into a water layer in the lower portion of the vessel and a hydrocarbon layer floating on said water layer, the vessel havingheating means in its lower portion in the waterlayer and a transverse partition member over the upper edge of which the hydrocarbon layer spills, the improvement which includes a transverse barrier member disposed in the vessel adjacent the upper edge of the partition-member, the barrier member having a horizontal upper edge disosed above theuppe redge of the partition niembeirand a horizontal lower edge disposed below the upper edge of the partition member and above the interface between hydrocarbon and water layers whereby the surface portion of the hydrocarbon layer is prevented from flowing directly to and over the partition member but hydrocarbons may flow from the layer under the lower edge of the barrier member and over the upper edge of the partition member.

8. A low temperature separation unit as set forth in claim 7 wherein the lower edge of the barrier member is disposed closely adjacent the heating means whereby hydrocarbons flowing under the barrier member are brought into close proximity to said heating means.

References Cited in the file of this patent UNITED STATES PATENTS 397,585 Coplen Feb. 12, 1889 6 Wingrove June 19, Frick June 17, Franks May 2, Maranville Feb. 2, Fisher Sept. 6, Morse Feb. 19, Lovelady et a1. Feb. 29, Walker Jan. 4, Glasgow June 28, Lind Oct. 4,

FOREIGN PATENTS Germany Sept. 25, 

1. A LOW TEMPERATURE SEPARATION UNIT INCLUDING THE COMBINATION OF, A VESSEL HAVING A FLUID STREAM INLET FOR ADMITTING TO THE VESSEL A FLUID STREAM CONTAINING LIQUID HYDROCARBONS AND HYDROCARON GAS HYDRATES, A LIQUID HYDROCARBON OUTLET FROM THE VESSEL SPACED A SUBSTANTIAL DISTANCE DOWNSTREAM FROM THE INLET, MEANS FOR MAINTAINING IN THE VESSEL A STRATUM OF WATER SEPARATED FROM THE FLUID STREAM, MEANS FOR MAINTAINING IN THE VESSEL A HYDROCARBON STRATUM FLOATING ON THE WATER STRATUM AND HAVING ITS SURFACE AT A SUFFICIENT ELEVATION TO FLOW INTO THE LIQUID HYDROCARBON OUTLET, MEANS IN THE LOWER PORTION OF THE VESSEL FOR SUPPLYING HEAT TO THE WATER AND HYDROCARBON STRATUM BETWEEN THE INLET AND OUTLET TO MELT THE HYDRATES THEREIN AND A BARRIER MEMBER MOUNTED IN THE VESSEL AND ISOLATING THE SURFACE OF THE HYDROCABON STRATUM UPSTREAM OF THE OUTLET FROM THE PORTION OF THE SURFACE OF THE HYDROCARBON STRATUM IMMEDIATELY ADJACENT THE OUTLET, THE BARRIER MEMBER EXTENDING ABOVE THE ELEVATION OF THE OUTLET AT ALL POINTS BETWEEN SAID OUTLET AND THE SURFACE OF THE HYDROCARBON STRATUM UPSTREAM OF THE OUTLET AND HAVING AT LEAST A PORTION OF ITS LOWER EXTREMITY TERMINATING IN THE HYDROCARBON STRATUM ABOVE THE INTERFACE BETWEEN THE HYDROCARBON AND WATER STRATA, WHEREBY HYDROCARBONS MAY FLOW UNDER THE BARRIER MEMBER TO THE OUTLET, AND A GAS OUTLET FROM THE VESSEL. 